survival_issue.R

library(survival)

##----------
## example 1
set.seed(123)
group <- factor(rep(LETTERS[1:2], each=100))
Xbeta <- c(-1, 1)[unclass(group)] + rnorm(200, 0, 2)
weibA <- 1.5
weibB <- 100
U     <- runif(200, 0, 1)
dat1  <- data.frame(tobs=ceiling((-log(U)*weibB*exp(-Xbeta))^(1/weibA)),
                    status=1, group=group)
fit1 <- survfit(Surv(tobs, status) ~ group, type="kaplan-meier", data=dat1)

## error
summary(fit1, times=2000)

##----------
## example 2
text <- 'tobs status group
1.18 1 B
1.15 1 B
0.20 1 A
0.08 1 A
0.27 0 A
0.02 0 B
1.09 0 A
0.80 0 B
0.63 0 B
0.67 1 B
0.10 1 B
0.30 1 A
1.03 1 B
0.18 1 B
0.12 0 A
0.38 0 A
0.74 1 B
0.09 1 A
1.95 1 B
0.75 1 A
0.10 1 A
0.10 1 A
0.15 1 A
0.08 1 A
0.34 1 B
2.43 1 B
0.45 1 B
0.09 1 A
0.41 1 A
0.21 1 A
0.44 1 B
0.02 1 A
0.12 1 A
0.28 1 A
0.02 1 A
1.26 1 B
0.15 1 A
0.41 1 A
0.05 1 A
7.08 1 B
0.32 1 A
1.32 1 B
0.74 1 B
0.04 1 A
0.76 1 B
0.03 1 A
0.23 1 A
1.19 1 B
1.47 0 B
0.54 1 A
0.59 1 A
1.02 0 B
0.15 1 A
0.12 1 A
0.40 1 A
0.60 1 B
0.32 1 A
0.37 1 A
1.54 1 B
0.18 1 B
1.03 0 B
1.43 0 B
0.75 0 B
0.04 1 A
1.98 1 A
1.00 1 B'

dat2 <- read.table(text=text, header=TRUE)
fit2 <- survfit(Surv(tobs, status) ~ group, data=dat2)

## result in different errors
summary(fit2, times=6)
summary(fit2, times=c(3, 6))

## sessionInfo()
## > sessionInfo()
## R version 4.0.0 (2020-04-24)
## Platform: x86_64-w64-mingw32/x64 (64-bit)
## Running under: Windows 10 x64 (build 18362)
## 
## Matrix products: default
## 
## locale:
## [1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252   
## [3] LC_MONETARY=German_Germany.1252 LC_NUMERIC=C                   
## [5] LC_TIME=German_Germany.1252    
## 
## attached base packages:
## [1] stats graphics grDevices utils datasets methods base     
## 
## other attached packages:
## [1] survival_3.2-2
## 
## loaded via a namespace (and not attached):
## [1] compiler_4.0.0 Matrix_1.2-18 splines_4.0.0 grid_4.0.0
## [5] lattice_0.20-41